Tire sizes and PSD
#1
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I know lots of us run different tire and wheel combos, but how much can you vary from spec before the PSD light comes on and senses differences in wheel speed from front to back. The reason I ask this is that I have 17" track wheels and want to run 245/40 and 275/40. The front diameter will be smaller than the rear...problem? Thoughts?
Roland
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#2
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I'm pretty sure the PSD only looks at left vs right. But ABS migth looks front / rear variation, but with the tires you want to run, I don't think you'll have a problem.
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PSD and ABS both look for front back difference too. It doesn't matter what size tires are as long as all four are similar size. I would keep front back variation within 5% difference from stock.
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Originally Posted by Vilhuer
PSD and ABS both look for front back difference too. It doesn't matter what size tires are as long as all four are similar size. I would keep front back variation within 5% difference from stock.
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I just read the manual. You're right. It does measure front vs. rear, but it doesn't intuitively make sense why that would be. Must be an engineering thing.
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Originally Posted by Andrew Olson
I just read the manual. You're right. It does measure front vs. rear, but it doesn't intuitively make sense why that would be. Must be an engineering thing.
http://www.youtube.com/watch?v=_PoocIsiV2c
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Neat video.
My '89 doesn't have that, but would running staggered sizes (255x50 & 225x50) mess up anything?
Not a lot of choices in 16's and thought a set of RA1's might be nice on the factory wheels sometimes.
Thanks.
My '89 doesn't have that, but would running staggered sizes (255x50 & 225x50) mess up anything?
Not a lot of choices in 16's and thought a set of RA1's might be nice on the factory wheels sometimes.
Thanks.
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http://www.miata.net/garage/tirecalc.html
Its right at the limit and could cause ABS system to raise error.
Code:
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 225/50-16 4.4in 12.4in 24.9in 78.1in 811 0.0% 255/50-16 5.0in 13.0in 26.0in 81.8in 775 4.8%